Based on our encouraging early results for primary stroke prevention in the SPIN Trial among children with SCA in Kano, Nigeria, we propose a definitive partial phase III trial with the same study team, wherein we will test the hypothesis that moderate dose HU therapy (20 mg/kg/day) results in 80% relative risk reduction when compared to low dose HU therapy (10 mg/kg/day) for secondary stroke prevention among children 1 - 18 years of age with SCA and acute overt stroke.